This invention lies in the field of injection systems for introducing various solid additives into a bath of molten metal and is directed particularly to such a system for simply and conveniently injecting solid additives into a bath of molten pig iron or steel while preventing the violent boiling and splashing which occurs with the use of conventional systems. It is simple in construction and reliable in operation.
In general, three systems of introducing additives have been used over a period of years. In one system, chunks of additive material have merely been thrown or shoveled into the bath. One of the major disadvantages of this technique is that there is a little advantage to adding increasingly stronger deoxidizers at progressive intervals during the tapping of the heat because of the high oygen content of the metal in the furnace.
Another system involves reducing the additive material to particulate form, entraining the particles in a stream of air or other gas, and forcing the stream into the bottom of the ladle or vessel through one or more apertures. When the gas is heated by the molten metal, violent boiling results and some of the metal is blown out the mouth of the vessel to endanger workmen in the area. Also, the inlet apertures are frequently plugged by solidifying metal when the bath is poured. In a modification, the stream flows through a pipe, or "lance," which is inserted down into the bath from above. The same boiling and plugging problems arise with this system.
In another variation, a similar pipe is mounted with its discharge end or nozzle spaced some distance above the bath and the stream is ejected down toward the bath with a velocity which drives the particles into the bath but is insufficient to force the gas beneath the surface. In this case the gas spreads out over the surface of the bath and causes violent churning motions which result in much splashing, although it is not as bad as the submerged gas discharges.